1. Field of the Invention
This invention relates to a mold-supporting arrangement in molding machines and specifically to molding machines used to mold rubber. Though disclosed in connection with the molding of rubber, the invention is applicable to the molding of other materials as well.
2. Description of the Prior Art
U.S. Pat. Nos. 4,459,909 to Takagi; 4,301,673 to Yonezawa; and 4,317,358 to Yonezawa et al, each disclose a molding press machine which includes roller arrangements to permit the molds or dies to be transported smoothly into and out of the press with a minimum of effort and a minimum of damage to the press. Applicant recognizes that in the usual rubber molding procedures, the molds are first loaded with rubber and then pushed into the molding press. The press is closed, the mold compressed, and, after curing, the press is opened and the mold withdrawn. In the larger presses, the molds are heavy and cumbersome to handle. Sliding the molds into and out of the press causes scoring, galling, and denting to the upper surface of the bottom platen of the press and to the undersurface of the mold. As disclosed in the aforementioned United States patents, the molds are more easily moved with reduced damage if load bearing units such as rollers or ball bearings are employed.
As noted in the Yonezawa et al, U.S. Pat. No. 4,317,358, the problems associated with die lifters which incorporate spring-loaded balls supported by heavy duty springs include: (1) the scoring and engraving of the mold by the ball surface; (2) undesired play between the mold and the platen; and, (3) drift of the balls in their supporting holes. The solutions to these problems proposed by Yonezawa et al are complex arrangements.
Further, the roller balls disclosed in these patents permit the mold to move laterally as the balls themselves can rotate in all directions.